The metabolic and physiological response of mammary carcinoma in the C3H mouse to combinations of photodynamic (PDT) and hyperthermia therapy will be investigated in vivo 31- P, nuclear magnetic resonance (NMR) spectroscopy will be employed to measure high energy phosphate metabolites and pH, response to PDT and hyperthermia. These measurements will be correlated with p02, and pH microelectrode measurements in the tumor and fixed biological endpoints. The tumor will be treated at the TCD level with PDT and will be subjected to hyperthermia at 43.5 degrees C at either TCD-10, TCD-10, TCD-50, TCD-90 values. The optimal time of application of hyperthermia after PDT will also be investigated. The goal of this study is to elucidate the therapeutic mechanisms of the combined therapy by documenting and providing a metabolic and physiological profile of tumor response over time.